AFTER THEY MARRIED IN 1989, Kenneth Branagh and Emma Thompson were dubbed the Golden Couple by the British press. But since their last appearance together, in Branagh's 1993 movie of Much Ado About Nothing, the actor-director and his actress wife have functioned more as two separate nuggets. Branagh, 34, directed a new movie comedy, In the Bleak Midwinter, opening in England on Dec. 1, and has just finished playing Iago in a film version of Othello (directed by Oliver Parker). He is also preparing to direct and star in a movie of Hamlet. The 36-year-old Thompson, meanwhile, has been filming two high-prestige British films, both due this fall: Sense and Sensibility, for which she wrote the script, based on the Jane Austen novel, and Carrington, about Bloomsbury painter Dora Carrington.

Apparently, there was just not enough contact between Branagh and Thompson. Or it may have been that there was too much between Thompson and her handsome Sensibility costar Greg Wise, 29, the son of distinguished British architect Douglass Wise. On Sept. 30, the day before Britain's News of the World ran a photo of Thompson making a morning departure from Wise's North London home, she and Branagh announced that they were bringing down the curtain. "It is with great sadness that we have decided to separate," they said in a statement. "Our work has inevitably led to our spending long periods... away from each other and, as a result, we have drifted apart."

The next morning, Thompson briefly faced reporters outside the couple's modest home in London's West Hampstead neighborhood. She admitted she felt "pretty ropy," or weary. When reporters asked her to repeat the couple's statement, she tried, but quickly gave up. "God, don't ask me," she said feebly. "I can't even string a sentence together."

There were clear signs of trouble in the marriage last January, when Thompson, suffering from exhaustion, spent two weeks at Grayshott Hall, a health clinic in Surrey. Branagh paid one visit, but Thompson reportedly told another patient, "He might as well have not bothered. I just want to sleep." Branagh, according to one British paper, moved out of the house some time ago. And in May, when Thompson showed up at the Cannes Film Festival to promote Carrington, she was with Wise.

Branagh and Thompson, who met while playing husband and wife in the 1987 BBC series Fortunes of War, may also have fallen victim to the vagaries of Hollywood. Her star has arguably outshone his. Thompson won the Best Actress Oscar in 1993 for Howards End and earned two nominations the next year. Branagh's recent efforts, on the other hand, include directing and starring in 1994's $40 million flop Mary Shelley's Frankenstein.

Another source of tension may have been Thompson's desire to start a family. Two years ago she told an interviewer, "I can hear my biological clock ticking away." Weeks later, she said, "Ken is so tired doing so many jobs. I should think all his sperms are on crutches." As their careers drove them further apart, Thompson stopped talking clocks. "I'm not feeling any pressure," she said in '94. In the end, the marriage ran out of time.

LYDIA DENWORTH in London